1. Field of the Invention
The present invention relates to a mould for moulding an elastomeric glazing profile in situ on a sheet of glazing material, and to a method for moulding the profile. It also relates to a glazing comprising a sheet of glazing material with an elastomeric glazing profile moulded on it; the glazing may be a vehicle glazing for glazing a vehicle window, e.g. a backlight for glazing a rear window.
2. Description of the Related Art
It is known to provide a unitary glazing comprising a sheet of glazing material with an elastomeric glazing profile moulded in situ on the sheet by a technique known as edge encapsulation. Materials in sheet form have two major faces and one or more peripheral edge faces, and as the term edge encapsulation implies, in this known technique, the material from which the profile is moulded extends over a marginal portion of one major face, over the peripheral edge, and onto the other major face. A simple mould for edge encapsulation generally comprises two mating segments which define the mould cavity together with the sheet of glazing material. Some of the glazings (xe2x80x9cpartsxe2x80x9d) required by vehicle manufacturers include an xe2x80x9cundercutxe2x80x9d portion, i.e. in cross-sectional view the part includes a recessed portion. The recessed portion (also known as a re-entrant portion) may be within the profile or at the meeting-point of the sheet glazing material and the profile. It is known to incorporate moving mould segments into the mould design for such parts, the reasons generally being either so that the mould can actually be machined in the first place, and/or so that the part can be removed after moulding. These moving mould segments are frequently termed xe2x80x9csliding coresxe2x80x9d, and an example is described in EP 156 882 B1 (corresponding to U.S. Pat. No. 4,561,625 and partially corresponding to U.S. Pat. No. 4,839,122) in column 5 at line 22 et seq. For some years, it has been an important consideration in the motor industry to reduce the fuel consumption of vehicles, and reducing the drag coefficient (i.e. the air resistance) of vehicles can make a significant contribution to this. One way to reduce a vehicle""s drag coefficient is to arrange the vehicle glazing to be flush with the bodywork to give the vehicle a smooth external contour; this is termed xe2x80x9cflush glazingxe2x80x9d. It will be appreciated that edge encapsulation as taught in EP 156 882 B1 is incompatible with flush glazing, because the portion of the glazing profile on the outside face of a window-pane protrudes from it. Vehicle manufacturers therefore demand that a glazing profile should be present on only one of the two major faces of a window-pane; these products are referred to as xe2x80x9csingle sidedxe2x80x9d.
Extrusion lends itself to the manufacture of such products, but is not without disadvantages. For instance, it is difficult (and requires expensive measures) to obtain a satisfactory joint between the beginning and the end of the extruded profile; materials suitable for extrusion which are also sufficiently durable to give an adequate service life are expensive, and one cannot extrude around a sharp corner.
Attempts have therefore been made to develop moulding techniques to make single sided products, and one example is known from WO 98/05487. However, some shortcomings remain, as will now be explained. A surface of a glazing profile which is visible when the glazing is installed in a vehicle is termed a xe2x80x9cshow facexe2x80x9d (this is normally the outward-facing surface). One consequence of the move to flush glazing is that the show face is no longer wholly positioned on the outside of the window-pane, rather, it may be at least partly positioned inwardly of the inside face, and is generally on a member such as a lip or tongue which extends beyond the inside face.
Frequently, the area of contact between the glazing profile and the pane is positioned adjacent the peripheral edge of the window-pane, but slightly displaced towards the centre of the latter. This results in a recess defined by the glazing profile and the pane together, i.e. the part includes an undercut. The recess is positioned adjacent the contact area between the pane and the profile on one side, and adjacent the peripheral edge of the pane on the other side. A conventional mould for such a part needs to include sliding cores to allow removal of the part, generally one per side so that a generally rectangular pane would require four sliding cores meeting at the corners.
Unfortunately it is usually the case that lines are left on the moulded profile at the joints where the sliding cores meet; with single sided moulding these mould lines are on the show face and hence objectionably visible. This was not so for the true edge encapsulated products made in the mould of EP 156 882 B1; although mould lines occurred, they were not positioned on the show face and hence could be tolerated. A related disadvantage of sliding cores is that the liquid moulding material may penetrate the joints and then set to a solid, i.e. limited leakage may occur. The resulting flap or fringe of elastomer (known as xe2x80x9cflashxe2x80x9d in the industry) on the curved profile must be removed, generally by a manual trimming operation, leaving a mould line as mentioned above. Furthermore, it is generally the case that the complexity of moulds with multiple sliding cores adds to their cost and makes them prone to such leakage.
It would therefore be desirable to mould a glazing profile in situ on a single face of a sheet of glazing material such that the profile is not susceptible to mould lines on its show face.
Accordingly, the present invention provides a mould for moulding an elastomeric glazing profile in situ on a sheet of glazing material having two major faces and a peripheral edge face, the profile having a show face, wherein the mould comprises a first mould segment and at least one further mould segment which are relatively movable into a position in which they are in intimate contact with each other, at least one of the mould segments being arranged to receive the sheet of glazing material, and the mould segments defining together with the sheet a mould cavity for moulding the profile on a single major face of the sheet, and wherein the portion of the mould cavity that moulds the show face is entirely formed by a single mould segment.
Normally the entire show face is moulded by a single mould segment. Designing the mould so that the show face is entirely moulded by a single mould segment clearly obviates the problem of mould lines on the show face, since there are no joints present on the mould surface defining the show face to yield mould lines. Furthermore, as the design is inherently simple, both construction and operation are facilitated, and the cost is reduced, compared with known moulds. Reliability is increased and leakage reduced. Moreover, the heavy press required for conventional edge encapsulation is no longer necessary, and the disadvantages of extrusion techniques are avoided.
The mould is especially useful for parts having undercut portions, i.e. re-entrant portions which would mechanically lock the part into a simple fixed mould (i.e. one without a moving mould segment). For such undercut parts, a corresponding portion of the appropriate mould segment is itself undercut.
The mould is also useful for parts having sharp corners, as it is not possible to extrude a profile satisfactorily around a corner having a radius of less than 20 mm, and radii of less than 30 mm present difficulties in maintaining the cross-section of an extruded profile. The reproducibility of corners of profiles may also be better with moulding than with extrusion.
Moulding possesses the further advantage over extrusion that it is possible to vary the cross-section of the profile around the glazing, e.g. to incorporate a high mounted stop lamp (also known as a third brake light).
Preferably, one of the mould segments is annular in form, at least in the vicinity of the mould cavity. This facilitates removal of the part after moulding.
The advantage of simplicity of construction and operation is maximised when the mould comprises a single further mould segment, so that there are just two mould segments in total. Note that the term xe2x80x9cmould segmentxe2x80x9d is used to refer to a component of the mould which provides part of the wall of the mould cavity; ancillary mould components such as retaining means for the sheet of glazing material (e.g. clamps or vacuum cups) or actuating mechanisms are not included.
In another aspect, the present invention also provides a method of making a glazing by moulding an elastomeric glazing profile in situ on a sheet of glazing material having two major faces and a peripheral edge face, the profile having a show face, the method comprising the steps of:
positioning the sheet of glazing material in a mould comprising a first mould segment and at least one further mould segment,
retaining the sheet in position with retaining means,
moving at least one of the mould segments relative to the others into a position in which they are in intimate contact with each other and together with the sheet of glazing material define a mould cavity for moulding the profile on a single major face of the sheet, wherein the part of the mould cavity that moulds the show face is formed entirely on a single mould segment,
injecting liquid resinous material into the mould cavity,
allowing the liquid resinous material to cure at least to the extent that it becomes solid,
moving at least one of the mould segments relative to the others into a position in which they are apart, and
removing the glazing from the mould.
Furthermore, it has been found possible to remove the glazing from the mould by temporarily deforming part of the profile to allow it to pass over one of the mould segments. This is especially advantageous when a part with an undercut portion is being moulded.
In a further aspect, the invention relates to a glazing comprising a sheet of glazing material having 2 major faces and a peripheral edge face, and an elastomeric glazing profile bonded to a single major face of the sheet, the profile having a show face, wherein the profile is formed by moulding it in situ on the sheet in a mould cavity of a mould comprising two or more mould segments wherein the part of the mould cavity that moulds the show face is formed entirely on a single mould segment.